GB1295348A - - Google Patents

Abstract

1295348 Plasma generators LA SOUDURE ELECTRIQUE AUTOGENE PROCEDES ARCOS SA 18 Feb 1970 [31 March 1969] 7835/70 Heading H5H Plasma flame apparatus for heating large areas of a workpiece comprises an anode body assembly having a plurality of spaced nozzle anodes 2 therein and at least one cathode 3 located opposite each nozzle orifice so that in use a plurality of spaced plasma flames 13 issue from the anode body assembly. The anode body assembly shown comprises an elongated copper or silver multiple anode 1 provided with a plurality of water cooled nozzles 2 insulated by plates 8 from tungsten cathodes 3 carried in a common insulating plate 5. The multiple anode 1 is connected to one side of a D.C. supply 4 and the cathodes 3 are connected in parallel to the other side. In Figs. 5 and 6 (not shown) the anode body assembly has a plurality of nozzle anodes insulated from one another by insulating spacers, each anode being connected to a separate supply (Fig. 5, not shown) or a common supply through an individual adjustable impedance, Fig. 6 (not shown). The arrangement shown in Fig. 1 may have its cathodes connected through independently variable impedances to a common supply (Fig. 4, not shown) or to separate sources (Fig. 5, not shown). Argon or neon is the plasma forming gas. Ignition may be achieved by momentary contact between the cathode and anode by means of a high frequency spark generator to initiate several arcs simultaneously, or preferably by a low frequency spark generator connected between the anodes and cathodes in succession. Such apparatus may be used for heat treatment, spraying refactory materials, nitriding and annealing broad moving workpieces. In Fig. 7 (not shown), two plasma flame assemblies of the type described are inclined with respect to one another so that their emergent plasma flames impinge at the surface of a moving workpiece. A.C. is passed from one multiple anode to the other via the plasma flames. A multiapertured powder hopper is provided between the multiple anodes. For tack welding the various arcs are struck at determined time intervals. In Fig. 9 (not shown), moving strip is heated by plasma "curtains" from transversely extending axially spaced multiple plasma assemblies and by internal resistance heating due to current passed through the strip via the plasma "curtains" from an A.C. source. This can be used for sintering cold rolled metal powders. By altering the impedance of the plasma flame from each nozzle, variations in heat treatment may be obtained across the strip. In Figs. 10 and 11 (not shown) the multiple anode assembly is annular, and the nozzle orifices are axially directed and equi-angularly spaced. This arrangement may be used to uniformly heat a monocrystal pulled along the axis of the annular multiple anode. In Fig. 12 (not shown), an annular multiple anode has a plurality of radially inwardly directed nozzles which heat a moving rod or bar during zone melting. A plurality of plasma "curtains" may be used as radiant heat or light sources e.g. as flood lights.